The use of dielectric materials to increase capacitance is well known and long-used. In the past, capacitor dielectrics have fallen into two categories. Dielectrics in the first category have a relatively temperature-independent dielectric constant but the value of the dielectric constant is low, e.g., 5-10. Materials such as electrical porcelain and mica fall in this category. Dielectrics in the second category have a high dielectric constant, e.g., 1000 or more, but they are quite frequency dependent. An example is barium titanate, BaTiO3.
Since capacitance is proportional to dielectric constant, high dielectric constant materials are desired. In order to perform acceptably in electronic circuits, a dielectric must have a dielectric constant that exhibits minimal frequency dependence. It is also desirable that the loss or dissipation factor of a dielectric be as small as possible.
Japanese Patent 2,528,117 B2 discloses superconducting materials of the formula (M1)x (M2)y (M3)zOw, wherein                M1 is B, Al, Ga, In, Tl, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu;        M2 is BE, Mg, CA, Sr, Ba, Ra, Sn or Pb;        M3 is Cu; and        x, y, z and w represents the molar ratio of the corresponding constituent elements.        
It has been found, however, that other Europium-containing compositions function well as dielectrics.